The invention relates in particular to electrochemical cells having an alkaline electrolyte and in which at least one of the electrodes includes a porous support or metal, e.g. nickel, filled with active material, e.g. based on nickel hydroxide.
Such a porous support has a matrix structure comparable to that of a sponge whose cells are connected to one another in a three-dimensional array that is referred to by the term "foam".
Prior to being filled with active material, the porosity of the foam is greater than 90%. In its initial state, the thickness e.sub.1 of the foam used generally lies in the range 0.5 mm to 5 mm, depending on circumstances.
An electrode plate of the above type is connected to a terminal of a cell via an electrode head which includes a connection zone that forms a kind of tab. Each connection tab is subsequently connected to the cell terminal by various means, such as screws, welding, etc. . . . .
Problems arise in the making of the electrode head with its connection tab. It is necessary for that region to be of sufficient mechanical strength, for it to provide good electrical conduction so as to take up all of the current generated over the entire surface area of the electrode, for it to avoid making the plate too heavy, and for it to be as simple and as cheap as possible to make.
Various solutions have been proposed for making said connection zone. For example, proposals have been made to rivet or staple a metal part to the foam of the support, other proposals have been made to compress the foam of the support as filled with active material, so as to provide a narrow tongue of same-kind foam that is unfilled, with the tongue extending along the entire height of the support and projecting upwards so as to form a connection tab.
The first solution is expensive and heavy, while the second is fragile and does not give full satisfaction with respect to quality of electrical conduction in the electrode head and in the projecting tab.